Protective apparatus for electrical circuits.



' PATENTED JAN. 8, 1907. H. P. DAVIS & P. CONRAD.

PROTECTIVE APPARATUS FOR ELECTRICAL CIRCUITS. urmoumn umzo 1004.

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ATTORNEY PATENTED JAN. 8, 1907.

H. P. DAVIS & F. CONRAD.

PROTECTIVE APPARATUS FOR ELECTRICAL CIRCUITS.

APPLICATION FILED JAN. 20 1904. I

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H I INVENTORS TORNEY UNITED PATENT OFFICE.

HARRY l. DAYlSfOF PITTSBURU, AND FRANK CONRAD, OF EDGEWOOD PAhK, PENNSYLVANIA, ASSIGNORS 'lOtdYES'llNUHOUSE ELEC"RI() & MANUFACTURING COMPANY, A CORPOlL-hllON 0F lENNSYLVANir-XQ PROTECTIVE APPARATUS FOR ELEdTiRICAL CIRCUlTS;

Specification of Letters Patent.

Patentedi fan. 8,1907.

Application filed January 20. 1904. Serial No. 189.903.

Be it known that we, HARRY P. Davrs, a resident of Pittsburg, and FRANK Coxrriro, aresident of Edgewood Park, in the county of Allegheny, State of Pennsylvania, citizens of the. United States, have invented a new and ttrs for Electrical Circuits, of which t lowing rs a specification.

()ur invention relates to apparatus for the protection of high tension transmission ines; and its object is to provide means for interrupting the circuit in a line when the current in any conductor of a line exceeds by not less than a predetermined amount the current in a corresponding conductor of an other line.

in transmitting electrical energy at high potentials over long distances it is a usual practice to employ two or more parallel lines. This is done for the purpose of avoiding the interruption of service which would occur in the event of an accident to a system embodying only a single line. It therefore be comes advisable to employ protective devices the operation of which will affect the injured line only.

Our invention is applicable to systems comprising one or more generating-stations from which the energy is transmitted to distributing-points by means of parallel lines, at either or both ends of which We propose to place devices which are operated only when the current of a given phase in one set of conductors exceeds by not less than a predetermined amount the current in another corresponding set. One or both ends of the lines may be protected also by means of ordinary overload devices. if desired.

Our'invention is illustrated in the accompanying drawin in which Figure 1 is a o rammatic view of a conplete three-phase rystem with the connections of the devicia properly made at one of the ends of the lines, andFig. 2 is a similar diagram of the connections of the devices at one end of a two-phase system. Fig. 3 represents a formv of transformer which is employed in connection with a circuit-breaker that is intendedto operate when the, currents in the parallel lines become unequal.

Referring now more particularly to Fig. 1, a three-phase generator 1 is shown as supplyting energy to loads comprising conductors l-conductors 7, n. and U. A loadS, comprisnrg' suitable translating devices, may be conuseiul Improvement in Protectrve Apparar re iols dcsir'crl point.

sidercd as supplied by a branch circuit whiclris connected to the main line at any At the generator end overload cir'cnit-br'calrcrs are indicated at 10 and 11 and rcversc-crrrrcnt breakers are indicated in the ends oi the branch and main lines at 12. Series transformers 13 and H, the primaries of which are respectively corrncctcd .irrt hc conductors 4 and T of the parallel lirrcsklrave their secondaries connected,

respectively, in series with coils l5 and l6 oi' anothcr transformer 17, a third coil lS'of which is energized only when the current in one oi the coils and 16 exceeds by a predetermined amount that in the other.

The coil 18 is connected to the currentwinding 19 of a specially-constructed instrument 20, which comprises, substantially, two ordinary wattnreters 21 and; 21 having their movable parts 22 and 22 mechanically connected. The voltage-winding 23 of the wattlneter 21 is supplied with energy though an intermediate transformer "2i from secondary winding 25 of a transformer 26, the primary winding 27 of which is corrnected between the conductors S and .l.

The transformer 24 is so constructed that an operating voltage may be maintained across the terminals of the voltage-windir g '23 of' the wattnreter 21 regardless of the fluctuations of the-voltage of the line. It conprises an iron core 28, having three legs 2?), 3t), and 31, in one of the outer ones, 29, of which is an air-gap 32, the other outer one, 31, being of reduced cross-section. The primary winding 33 is placed upon the middle leg 30 and the secondary winding-3+ upon the outer leg 31, having the reduced cross-section. The iron core at ordinary voltages is ox-ersaturated, the extra llux being forced across the air-gap 32. 1f the voltage in the line drops considerably, there rs still sullicrentllux in the outer leg 31 oi reduced cross-section to maintain an approximately constant voltage at the terminals of the secondaryir'inding 34.

windings 151 and 23 are substantially like those described for transformers 13, 14, 17,

24,-and 26 and windings'19 and 23 and need not here belrepeated; The transformer '17, upon which the coils 15,,1'6, and18 are wound,- is also specially fconstructedin order that energy may be supplied to the winding 18 only when the currents in corresponding parallel conductors are unequal. The core 350i this transformer comprises laminae of substantially the same form as are used in trahsformers of the shell type, the three coils 15,16, and18 being placed upon the middle leg36 with the winding 18-between-windings16-and 1.6. 'VVith this arrangement "it the current in either'of the coils 15 and 16 exceeds by a predetcrmined amount that the other the resulting flux energizestheiwinding 18. A similar result occurs ifthe direction of 'the drop of potential through either of the windings 15 and 16 is reversed fromits normal direction. i The instrument 20, which com. rises watt 'meters 21 and 21, is-providedor thepurnose ofselecting the line upon which a shortv circuit or other accident mayhave occurred and for causing other. suitable apparatus to by supp operate to out thatjlin'e out of service. It being desirable to-employa circuit-closing device that shall be responsive only to differences 1 between the.-currents in a the two lines, we have utilized the well-known wattmeter principle toproduce two rragnetidfields that are of different phasein order to actuate'the movable member mounted within their co m.-

bined influence and havemade-tlieoperation solely dependent upon difference. in currents ying a substantially co stant vltageto one ofthe windings and stipplying-no pnergy to theother-windingexce t'whenthe' proper actuating conditions ex st. 'Iii the current traversing thetransformers 13 and 13 exceeds by a predeterrninedamount that traversing the corresponding transformers 14 and 14 wattmeter-needle 37 is-brought-into engage merit with: the one. or'the other of contact-terminals38 and 39 and a circuit iscon;- v pleted'through-battery LO-and theg one-or the other ,of circuit-breaker tripping-coils 41 and 42,'according to the lineon which the short circuith-as occurred. I:

'lt 'is-toibe understood that any dth'er suitable device may be em loyed which will satisifactorily indicate the injured line nd cause t to be thrown-outof service, the. specific type of-dnstrument here shown forming-nope rt ofour present invention. I

' The-operation of the system maybe understood by assuming, for example, a short ircuit at 43 between conductors 4 and 5. The circuit-breakers ,at 10, being ordinary overload -devices,=.wlll open because of the excessive current through them -a-nd the-short circuit.

i'lifl'ercnt amounts of current traverse" the icuit-breaker tripping-coil 41, and the line. comprising conductors 4, 5,'an d .6 is cutout connected in the conductors 45 and 46'of one 'tors 44 and 45 and between conductors As a result of the short circuittransformers 13 and 14 and-the windings'lS I and 19 are energized, thereby causing needle 37 to engage contact-terminal Acir'cuit is then completed through battery 40 and cir-x of service. The apparatus operates si1ni-.

larly for a' short circuit between any other I of the parallel distributingdine and the priniary windings of the transformers l i-and 14 are respectlvely connected 111 a snnllar imanner in 'thecon'ductors '51 and 48 of the" other line, the secondary windings being re-- spectivelyconnected to the primary windings 15, 15, 16-, and 16 of the relaytransiormers,"

the secondary windings 18 and 18 of which lare connected to the special instrument 20, as-

in the threephase system. 'Thecomiections =0f the special transformers 24 and 24 to .the voltage-windings 23 and 23*0f the instru- 'ment 20 are also similar to'those shown for the three-phase system, energy being supplied thereto from the 'transformers26 and 26", the primary windings of which are-connected, respectively, between the c'onduc-Q .and49. I 5 :1 .It is evident that we have provided such' '5 means for protecting arallel transmission lines that, an injured in'e or'one on whichafs short circuit may have occurred Inaybe automaticallyisolated or cut out'withou-t disturbing a parallel line, and ,We do not wish ourinvention to be limited except by such restriations as 'are imposed by thepriorart.

It is to be also understood that ourinv'en, tion is not limited to the employment of a single generating-station for the parallel I lines, since the number andlocation of generatingstations may be varied in accordance with the lengths of the transmissionlines. andother conditions of service.

' 'We claim as our invention I 1. The'co'inh'fnati n, 1n an alternating-current systembf electrical distribution having paralleldistributing-lines and circuit-breakers in one or both of thecnds thereof, of means for selecting and energizing'the tripping-coil of the proper circuit-breaker comprising-a relay-transformer havingtwo primary windings which are respectively energized by currents. proportional to the currents in the distribut- -1ng-oonductors and which normally induce- 2. The combination, in an alternating-current system of electrical distribution having parallel distributing-lines, with circuit-breakers in either or both ends thereof, and electromagnetic means for selecting and energizing the tripping-coil oi the proper circuitbreaker, of means for energizing said selecting apparatus comprising a transformer havequal. amounts and a secoi'idary winding which is energized by the resultant of the primary fluxes.

3. The combination, in an alternating-current system of electrical distribution having parallel distributin g-lincs, with circuit-breakers in. either or both ends thereol', and electro magnetic means for selecting and energizing the tripping-coil of the proper circuit-breaker having current and voltage windings, of means for energizing the voltage-windings of said selecting apparatus with an approximately constantvoltage comprising a trans former having a magnetically-satnrated iron core and a leakage-pathfor the flux.

4. A system of electrical distribution comprising a generating-station, parallel distrib- I 0 0 v uting-lmes, circuit-breakers near the distributing ends of the lines havlng tripping-coils,

an auxiliary circuit therefor, series trans formers having primary windings in series with conductors of the distributing-lines, a relay-transformer having primary windings connected to the secondary windings of said series transformers and normally producin opposing fluxes in approximately e ua amounts and a secondary winding whic is energized by the resultant of the primary fluxes.

v 5. The combination, in an alternating-current system of electrical distribution having parallel distributing-lines, with circuit-breakers in one or both ends thereof and means for selecting and energizing the tripping-coil of the proper circuit-breaker, of means for energizing current-windings of said selecting ap- 1n tworimar Y wmdnws which normally aratus com )I'lSln" rela -transformers each R: o. n produce opposing fluxes 1napproxnnately having two primary windin s receiving energy respectively proportiona to that flowing in corresponding conductors of parallel lines and secondary windings which are energized only when the current in one of said primary windings exceeds by more than a predeter mined amount that in thelother of the same transformer and which are in series with said current-windings.

In testimony whereof we have hereunto subscribed our names this 12th day of J anuary, 1904.

HARRY P. DAVIS. FRANK CONRAD.

Witnesses:

CAROLINE SMYERS, 'BIRNEY HINES. 

